1. Field of the Invention
The present invention relates to a process for increasing the production of benzene from a hydrocarbon mixture. More particularly, the present invention pertains to a process for increasing the production of benzene by integrating a process for producing an aromatic hydrocarbon mixture and liquefied petroleum gas (LPG) from a hydrocarbon mixture with a solvent extraction process for separating and recovering polar hydrocarbons from the hydrocarbon mixture.
2. Description of the Related Art
Generally, aromatic hydrocarbons are obtained by separating a feedstock fraction, which is rich in aromatic compounds, such as reformates produced through a catalytic reforming process and pyrolysis gasolines produced through a naphtha cracking process, from non-aromatic hydrocarbons using a solvent extraction process. The aromatic hydrocarbon mixture thus obtained is separated into benzene, toluene, xylene, and C9+ (compounds having 9 or more carbons)aromatic compounds using a difference in boiling point to use them as basic petrochemical materials, and the non-aromatic hydrocarbons are used as a feedstock or a fuel for the naphtha cracking process.
With respect to this, U.S. Pat. No. 4,058,454 discloses a solvent extraction process for separating and recovering polar hydrocarbons from a hydrocarbon mixture containing the polar hydrocarbons and nonpolar hydrocarbons. Most solvent extraction processes, as well as the above patent, take advantage of the fact that all aromatic hydrocarbons are polar. That is to say, if a solvent capable of dissolving polar material, such as sulfolane, therein is added to a hydrocarbon mixture, polar aromatic hydrocarbons are selectively dissolved and thus separated from nonpolar non-aromatic hydrocarbons. This process has an advantage in that it is possible to produce a highly pure aromatic hydrocarbon mixture, but is disadvantageous in that an additional solvent extraction device is necessary and a solvent must be continuously supplied during operation. Accordingly, there remains a need for a process for separating aromatic hydrocarbons and non-aromatic hydrocarbons from feedstock oil without an additional solvent extraction step.
In connection with this, effort has been made to employ another reaction system instead of a solvent extraction process in order to separate aromatic compounds from non-aromatic compounds. The non-aromatic compounds which are mixed with the aromatic compounds are converted into gaseous hydrocarbons through a hydrocracking reaction using a catalyst, and the aromatic compounds and the non-aromatic compounds are separated from each other using a gas-liquid separator at a rear part of a reactor. This technology has been developed from U.S. Pat. No. 3,729,409.
Furthermore, a process for producing aromatic hydrocarbons and LPG from a hydrocarbon mixture, in which aromatic compounds of the hydrocarbon mixture are converted into a fraction including benzene, toluene, xylene and the like through dealkylation and/or transalkylation reactions, and non-aromatic compounds are converted into gaseous material that is rich in LPG through a hydrocracking reaction, has been studied.
The above-mentioned processes, respectively, which have the common object of producing aromatic hydrocarbon products, such as benzene, toluene, or xylene, have been independently developed as competitive, or complementary/substitution technologies. However, a process for improving productivity of aromatic hydrocarbons, particularly, benzene, by integrating competing processes has not yet been suggested.